Electrical signals of a patient have a great diagnostic value as to the state of the patient. Accordingly, some devices detect and measure such signals, for example by using electrodes.
This detecting and measuring is challenging for a number of reasons. First, these electrical signals are very small in the first place, and are further vulnerable to interference by other ambient signals that include radio frequency signals, triboelectric interference, artifacts from torso movement, and so on. The interference is manifested as electrical noise that becomes superimposed on the signal, which prevents accurate detection and measurement.
Second, the electrode's electrical contact with the patient's skin is not ideal, and can present high electrical resistance and/or impedance. This problem has been solved in some instances by applying a gel between the skin and the electrode. The gel contains an electrolyte that facilitates conduction and reduces impedance.
Although the gel solution works well in emergency situations, it is a problem in situations where the electrodes are going to be worn for a long time. Examples include wearable defibrillators, devices worn on the wrist, chest, neck, head, and so on.